Bug 13891: DataTables server-side processing - Fix regressions

Bug 13891: DataTables server-side processing - Fix regressions

This patch fixes the regressions introduced by the previous patches.
If you have tested all in once, you didn't see them.

It introduces library, category and "first letter" filters.

Test plan:
1/ On all pages impacted by previous patches + new order empty (link patron to
an order) + guarantor search
2/ Add / Select patron to the list
3/ Use the filters
4/ Confirm there is no regression

Tested together with other patches.
Signed-off-by: Marc Veron <veron@veron.ch>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>